Organic polymeric materials such as plastics and resins, are subject to thermal, oxidative and photo-degradation. A great variety of stabilizers are known in the art for stabilizing a diversity of substrates. Their effectiveness varies depending upon the causes of degradation and the substrate stabilized. In general, it is difficult to predict which stabilizer will be most effective and most economical for any one area of application. For example, stabilizer effectiveness in reducing volatility may depend upon preventing bond scission in the substrate molecule. Limiting embrittlement and retaining elasticity in a polymer or rubber may require prevention of excessive crosslinking and/or chain scission. Prevention of discoloration may require inhibiting reactions which yield new chromophores or color bodies in the substrate or stabilizer. Problems of process stability and incompatibility must also be considered.
It has now been determined that the (hydroxyphenylthio)succinic anhydride or succinate derivatives of this invention possess an unusual combination of desirable properties which makes them particularly effective and useful as stabilizers. The compounds are particularly effective in protecting high impact polystyrene, rubbers such as polybutadiene and styrenebutadiene rubber, and other elastomers wherein retention of elasticity and inhibition of crosslinking, crazing, discoloration, odor formation and exudation are basic requirements.